The present invention relates to a battery with on-board load leveling and, more particularly, to the integration of at least a battery with at least a supercapacitor and miniaturized electronic controllers within a single housing, wherein the supercapacitor provides load leveling to the battery at charging and discharging.
Batteries are indispensable in the modern life. From automobiles and cellular to lap tops and PDA″s, the devices will not perform without batteries. Batteries are generally categorized as primary batteries that offer only one time of use, and secondary batteries that can be reused through electrically recharging in a number of cycles. As chemical reactions coupled with structural alteration are involved in the energy transfer of batteries, they are all limited in the rates of charge and discharge, as well as the depth of discharge. High power density and rapid recharge-ability are thus two goals in the incessant developing endeavors for batteries.
On the contrary, although capacitors have superior power density, depth of discharge, and recharge-ability than battery for the energy transfer occur only on the electrode surface of capacitors. Nevertheless, as the bulk of electrodes is not utilized for storing energy capacitors have an inferior energy density than batteries. To improve the energy density thus becomes the major developing target for capacitors. Obviously, an ideal energy-storage device should combine the advantageous qualities of both batteries and capacitors. Just like lead acid battery has the greatest power density among commonly used batteries including Ni—Cd, Ni—MH, Li, and Zn—air, supercapacitor has the highest volumetric energy density among all capacitors including ceramic, plastic film, aluminum electrolytic, tantalum, glass, and mica capacitors. Because of its high energy content, supercapacitor is capable of delivering and receiving currents up to hundreds of Ampere that impart the capacitor practical values to provide load leveling to batteries and fuel cells for power applications.
It is a paradox for an energy-storage device to simultaneously possess both of high energy density and high power density. As high energy density requires thick electrodes, whereas thin electrodes are needed for high power density. The device can be achieved only when a material with nanometer dimensions and a high energy capacity together with an implementing method, which can exactly convert the material into electrodes without losing the distinctive characters of the material, can be established. Otherwise the ideal energy-storage device is hardly attainable. While enthusiastic endeavors are dedicated to the discovery of the aforementioned material and method, there are hybrid designs proclaimed for enhancing the energy capacity and/or the energy efficiency of batteries and capacitors. In U.S. Pat. Nos. 4,959,281, 6,088,217, 6,222,723, and 6,252,762, also reports by Drews et al. “High-rate lithium/manganese dioxide batteries; the double cell concept”, J. Power Sources, vol. 65, pp 129–132, 1997, and by Arbizzani et al., “New trends in electrochemical supercapacitors”, J. Power Sources, vol. 100, pp 164–170, 2001, as well as by Pasquier et al. “A Nonaqueous Asymmetric Hybrid Li4Ti5O12/Poly (fluorophenylthiophene) Energy Storage Device”, J. Electrochem. Soc., vol. 149, no. 3, pp A302–A306, 2002, wherein a battery electrode is used as anode and a supercapacitor electrode as cathode to construct hybrid devices. By properly selecting the hybrid pairs, it is said that the energy density of an asymmetric supercapacitor is increased by six times as stated in U.S. Pat. No. 6,222,723. Even with 10-fold augmentation in the energy density of supercapacitor, its energy content is still tiny in comparison to that stored in batteries. In addition, neither the battery electrode can be protected against over-charge and over-discharge by the capacitor electrode, nor can the capacitor electrode completely utilize all the increased energy for providing peak currents as the reaction on the battery electrode is slow as usual. There is no practical gain in the asymmetric devices.
It is known in the art that batteries should have protection mechanisms and electronic circuits against high internal pressure, run-away temperature, inverse polarity, over-charge, and over-discharge. Normally, batteries and their protection means are two separate identities in different packages. However, for fast and precise performance, mechanics and electronics are now being integrated into a single device known as mechatronics that can be found in products such as computer disk drive, dryer, air bag, CD/DVD player, and automobile braking system. Such concept has been applied to the construction of integrated batteries as well. U.S. Pat. Nos. 4,622,507, 5,644,207, 5,645,949, 6,020,082 and 6,163,131 all disclose the integration of batteries with control circuits in a single housing. They are incorporated herein by references in their entirety. By placing the controllers by the batteries within a single casing can provide a number of advantages including fewer connecting cables used, close monitoring, EMI (electromagnetic interference) shielding, and real-time response. An electronic controller should modulate at least the following four key functions of batteries: 1) use time, 2) power output, 3)recharge time, and 4)safety. The first two functions relate to the discharge of batteries on driving various loads. U.S. Pat. No. 6,163,131 has allocated one-quarter of its entire content to a discharge sub-controller wherein the energy utilization of batteries is enhanced via safe deeper discharge. In essence, using electronic controllers alone for improving the qualities of batteries is a passive approach. Though the electronic controllers can protect the batteries from damages due to excessive charge and discharge, the circuits merely regulate and guide the batteries to execute energy transfer under some predetermined levels. On one hand, the controllers contain no energy to help batteries to meet great power demands, on the other the controllers can not assist batteries to receive large energy as generated in the regenerative braking of electrical vehicles. The controllers just block excessive energies instead of retrieval. To provide a realtime load leveling and to save all available energies, the present invention integrate batteries, supercapacitors and electronic controllers within a single housing.